1. Field of the Invention
The present invention relates, in general, to a multi-angle clamp, and more particularly, to a multi-angle clamp for use in an external fixation system for holding, distracting and compressing bone fragments adjacent to each other.
2. Description of Related Art
In various orthopedic surgical procedures, it is often necessary to secure two or more portions of bone in a relatively fixed relationship to each other. This need is often a result of a fracture which has occurred to the bone. To ensure that the bone can properly regenerate and fuse the fractures of the bone, it is important that the various bone fragments be positioned at the desired location during bone regeneration.
External fixation systems have been developed to compress two bone fragments for effective healing. Such systems can also be used to distract an osteotomy to achieve bone lengthening. In distracting bone fragments, the separation of the bone fragments must take place along a line parallel to the axis of the bone. Additionally, during such a distracting procedure, the surgeon reorients the pins of the external fixation system over time to achieve the desired bone lengthening.
An example of a typical external fixation system is a rail fixation system. Such a rail fixation system includes two clamps positioned on a rail member. In most instances, one of the clamps is stationary and one of the clamps is adjustable. The clamps are used to secure pins that are coupled to bone fragments.
A common problem encountered by the surgeon is orientation of the pins of the two clamps. If the clamp cannot rotate or pivot, all of the pins must be inserted in the same plane and must be parallel to each other. This condition restricts the surgeon in the selection of the best insertion region on the bone for the pins. In addition, it is very difficult and requires a high amount of skill for a surgeon to orient two or more pins exactly parallel to each other in a single plane. In order to alleviate this problem, rail fixation suppliers developed clamps that allow for rotation of the pin holder. This allowed the pins to be oriented in a non-parallel manner; however, the pins still needed to be in the same plane. Accordingly, rail fixation suppliers developed articulating rails. Such rails are adjustable through a joint that allows for one-dimensional pivoting or ball and socket articulation. This added feature allows the surgeon to position the pins in the clamps with less restriction.
An example of such an external fixation system is described in U.S. Pat. No. 5,951,556 to Faccioli et al. This reference discloses a compact external fixation device for the treatment of bone fractures. The fixation device comprises a pair of clamps connected to a central body by respective spherical joints. The spherical joints include a ball that is configured to cooperate with a cavity in each of the clamps. The clamps are designed to clamp bone screws or pins that have previously been surgically inserted in stumps of a fracture.
However, such structures suffer from a variety of limitations. For example, external fixation systems as described above are less rigid, heavier and more costly than external fixation systems that are constructed from a single rail.
Another type of external fixation system is a ring fixation system. In such a system the pins are used primarily to transfer the patient's weight from the foot or ankle to the tibia. The individual pins are seldom inserted in the same plane or parallel to each other. Additionally, in some instances, the rings are tilted in order to control the angle between two bone segments or across a bone joint in order to correct for acquired or congenital bone deformity. The point of insertion of the pins into the patient is critical. Currently, the pins are secured to the ring fixation system by a pin bolt. However, the surgeon needs greater flexibility in orienting each pin beyond the rotation in one-plane that a pin bolt can provide.